Noncontact cargo detector

ABSTRACT

A small chemical substance detecting device capable of detecting, by transmitting a radio wave, the NQR of an atom contained in a chemical substance by means of a high-temperature superconducting SQUID magnetic sensor exhibiting a high sensitivity even at a low frequency without unsealing the chemical substance contained in a package or a container. The detecting device can also identify the chemical substance at the same time.

TECHNICAL FIELD

The invention of this application relates to a detecting device isinspecting a baggage and, more particularly, to a noncontact baggageinspection device capable of inspecting contents of a baggage or hagscontaining a chemical substance such as a narcotic or an explosivewithout opening it up.

BACKGROUND ART

At the time of entry in and exit from a country, generally speaking,checks are made not only by a metal detector but also for chemicalsubstances such as narcotics. A number of baggage inspection deviceshave been developed (for example, in Cited Publications) for preventingthose drugs from being carried into or out of a country.

However, even at present, the detection of chemical substances such asthe drugs mostly depends on the sense of smell of dogs. However, fewdogs have such a special ability, and it takes a long time to train suchdogs. Thus, it is the present situation that no country can sufficientlycope with the increasing smuggling of drugs.

Publication i: JP-A-2001-091661

Publication 2: JP-A-2002-098771

Publication 3: JP-A-2000-028579

Publication 4: JP-A-07-333351

The method for detecting drugs of such chemical substances isexemplified by a nuclear magnetic resonance method (magneticcharacteristics), a neutron method (radioactivation characteristics), achemical method (bonding state of atoms), a biological method (using anantibody bio-film) and so on. Among these, the nuclear magneticresonance method is excellent for its processing ability.

This nuclear magnetic resonance method generally used is the so-called“NMR method” (Nuclear Magnetic Resonance Spectrometer), and is utilizedat present mainly in medical devices such as MRI (Magnetic ResonanceImaging) devices.

The chemical substance detecting method utilizing the nuclear magneticresonance, the NMR method, utilizes the phenomenon that the nuclearmagnetic moment in a chemical substance resonates with a high frequencywave in a magnetic field, and can detect the kind of the chemicalsubstance directly. For this NMR method utilizing the nuclear magneticresonance, however, a large-sized device is indispensable for generatingan intense magnetic field, and the NMR method has a fatal defect in thelarge size of the device.

Therefore, the invention of this application has an object to solvethese problems of the chemical substance detecting devices of the priorarts.

DISCLOSURE OF THE INVENTION

In order to solve the aforementioned problems, according to theinvention of this application, there is firstly provided a noncontactbaggage inspection device characterized by comprising: anelectromagnetic wave transmitting device including an electromagneticwave transmitter and an electromagnetic wave transmitting antenna; and ahigh-temperature superconducting SQUID for receiving the NQR of nitrogenatoms resonating with the transmitted electromagnetic wave. Theinvention provides secondly a compact noncontact baggage inspectiondevice characterized by comprising a chemical substance detectorincluding an electromagnetic wave transmitting antenna and ahigh-temperature superconducting SQUID; an electromagnetic wavetransmitter; a high-temperature superconducting SQUID controller; and adata processor; thirdly a noncontact baggage inspection devicecharacterized in that the electromagnetic wave transmitting antenna andthe high-temperature superconducting SQUID are disposed in a magneticshield; and in that an endless belt can pass through the inside of themagnetic shield; fourthly a noncontact baggage inspection devicecharacterized in that the magnetic shield is a metal box having a highmagnetic permeability; and fifthly a noncontact baggage inspectiondevice characterized in that the cooling medium of the high-temperaturesuperconducting SQUID is liquid nitrogen.

Moreover, the invention of this application provides sixthly anoncontact baggage inspection device characterized in that thetransmitted electromagnetic wave is in the radio frequency band of 0.1to 10 MHz; seventhly a noncontact baggage inspection devicecharacterized in that the electromagnetic wave transmitting antenna hasdirectivity; and eighthly a noncontact baggage inspection devicecharacterized in that a square wave is transmitted from theelectromagnetic wave transmitting antenna, and the frequency spectrumobtained by the quick Fourier analysis of the signal detected by thehigh-temperature superconducting SQUID is compared with the spectraldistributions of chemical substances in a database.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an entire noncontact baggage inspection device.

FIG. 2 shows the concept of chemical substance detection utilizing NQR.

FIG. 3 is a diagram showing the relation between frequency andsensitivity.

Here, reference numerals in the drawings designate the followingcomponents.

-   1 Radio Wave Transmitting Antenna-   2 Amplifier-   3 Radio Wave Transmitter-   4 SQUID Electronic Circuit-   5 Lock-In Amplifier-   6 Data Processor (Personal Computer)-   7 SQUID-   8 Liquid Nitrogen Container-   9 Double Magnetic Shield (with Cylindrical Upper Cover)-   10 Double Magnetic Shield (with Mounting Hole In Upper Portion)-   11 Belt Conveyor-   12 Baggage (Article to Be Inspected)-   13 Baggage Entrance-   14 Baggage Exit

BEST MODE FOR CARRYING OUT THE INVENTION

The invention of this application utilizes the phenomenon that whenthere is a electric field gradient around nitrogen 14 atoms, theyresonate along with a low-frequency radio wave, thus allowing detectionof the nitrogen 14 atoms existing in a chemical substance. According tothe principle of this chemical substance detecting device, a radio waveis transmitted, and the nuclear quadrupole resonance (“NQR”) to aparticular frequency of radio wave, intrinsic to nitrogen 14 atoms(14N), is detected.

The invention of this application is characterized by utilizing asuperhigh-sensitivity magnetic sensor, the superconducting quantuminterference device (abbreviated “SQUID”), for detecting thelow-frequency band, which has been especially difficult for theelectromagnetic wave detecting coil employed in the prior arts todetect.

The chemical substance detecting device combining the NQR and thehigh-temperature superconducting SQUID will here be schematicallydescribed. First, a radio wave is transmitted from a radio wavetransmitter through a radio wave transmitting antenna. For example, whenthe baggage/article to be inspected is irradiated with the radio wave,the nitrogen 14 atoms existing in the TNT (Trinitrotoluene) employed asan explosive are caused to transmit the NQR signal by the radio wave,and the NQR signal is received by the high-temperature superconductingSQUID being cooled with liquid nitrogen. Then, the data processorcompares the NQR signal with the existing resonance frequency thereby todetect the chemical substance contained. The method employing a NQRsignal in the invention of this application for detecting a chemicalsubstance uses a principle like that of the NMR (Nuclear MagneticResonance Spectrometer) in common use. The essential difference betweenthe NQR and the NMR is that the NMR rises in magnetic field, whereas theNQR rises in an electric field gradient around an atomic nucleus so thatNQR is excellent for identifying a substance even in a zero magneticfield.

The principle of the NQR to be used in this device is shown in FIG. 2.

As shown in this schematic diagram of FIG. 2, the chemical substance isidentified by the resonance vibration intrinsic to a molecule,determined by the unique electric field gradient of the molecule, inthis case nitrogen 14. Nowadays, the resonance frequencies intrinsic toseveral hundreds of thousands of chemical substances have already beenexamined to make it easy to detect the target chemical substance. Therange of the electromagnetic wave usually to be employed for detectingthe NQR is a radio wave of 10 MHz or less.

In case a target chemical substance exists nearby, it is detected bybringing the electromagnetic wave transmitting antenna close to thechemical substance. In case the chemical substance is remote, thedetection can be made by using a electromagnetic wave transmittingantenna with directivity.

Thus, the chemical substance is detected. However, this resonancefrequency of the NQR signal is generally only a few MHz (Megahertz),which is lower than that of the ordinary NMR. This raises the problemthat the electromagnetic wave detecting coil usually employed cannotdetect the target substance sufficiently. The relation between thatfrequency (f) and the reception sensitivity are shown in FIG. 5. It isclear from FIG. 3 that the NQR reception sensitivity of theelectromagnetic wave detecting coil is seriously lowered in thelow-frequency band but that the SQUID sensitivity is constant,independent of the frequency (f).

The invention of this application is proposed to eliminate the abovedefect, receiving the NQR reliably by means of a high-temperaturesuperconducting SQUID detector in the frequency band of the NQR that theelectromagnetic wave detecting coil cannot detect sufficiently.

This SQUID is a high-sensitivity magnetic sensor applying thesuperconducting quantization, and has a sensitivity one hundred times ormore higher than that of the magnetic sensor of the prior art so that itcan detect a weak magnetic field one fifty millionth that of the earth'smagnetic field.

In the invention of this application, it is preferable to employ not theusual SQUID using helium as a cooling medium but a high-temperaturesuperconducting SQUID. This is because the SQUID of the prior artemploying liquid helium as the cooling medium not only is hard to handlebut also has the difficulties of high cost for the liquid helium and thelarge size of heat insulation needed. Thus, it is likely difficult toutilize this SQUID in a portable chemical substance detecting device.

On the contrary, the high-temperature superconducting SQUID is easy tohandle and can employ the liquid nitrogen (at 77.3 K: −196° C.) at a lowcost so that it can be made small and light, thereby making thenoncontact baggage inspection device compactly.

In the invention of this application, therefore, the SQUID is thehigh-temperature superconducting SQUID which can be cooled down with theliquid nitrogen. However, the superhigh-sensitivity magnetic sensorutilizing this SQUID is so extremely sensitive as to invite a problemthat the actually used chemical substance detecting device may pick upenvironmental noise.

This environmental noise can be efficiently eliminated by providing amagnetic shield for shielding the environmental noise. This magneticshield is composed of double magnetic shielding plates and configured toexpel the NQR signals transmitted from objects other than the targetbaggage (the inspection target). Thus, the invention of this applicationdetects a chemical substance in a package or a container in a noncontactmanner. Here, the chemical substance detecting device of the inventionof this application is characterized in that it can identify and detecta plurality of substances simultaneously by changing the frequency. Theband of the frequency at this time should not be especially limited butpreferably is 0.1 to 10 MHz.

As has been detailed hereinbefore, the chemical substance detectingdevice of the invention of this application has many featuresdistinguishing it from other chemical substance detecting devices. Theexcellent features of the invention of this application may beenumerated as follows.

(a) The device can detect the chemical substance itself directly.

(b) The device can detect a plurality of different chemical substancessimultaneously by changing the frequency.

(c) The device can be made small and portable.

(d) The device needs no magnetic field for detection.

(e) The device can perform a high-sensitivity measurement by using theSQUID as the sensor.

(f) The device can operate with just a small quantity of liquidnitrogen, by utilizing the high-temperature superconducting SQUID.

The invention of this application has the features described above, andis described below in detail in connection with its Embodiment.

EMBODIMENT

As shown in FIG. 1, this magnetic shield is constituted to include: arectangular magnetic shield (10) of a double structure provided with anentrance (13) and an exit (14) for a baggage (inspection target)upstream and downstream respectively of a belt conveyor (11 ); and adouble-cylinder magnetic shield (9) over an upper through hole in theupper wall of the rectangular magnetic shield (10). The belt of thenonmagnetic belt conveyor (11) can run within the rectangular magneticshield (10). It is natural that the drive rollers or the motor of thebelt conveyor (11) are disposed outside of the magnetic shield (10).

In the cylindrical magnetic shield (9), there is disposed a liquidnitrogen container (8), in which a SQUID (7) is dipped.

A baggage (inspection target) (12) carried on the belt conveyor (11) isintroduced from the baggage entrance (13) into the magnetic shield (10).Then, a radio wave transmitted from a radio wave transmitter (3) isamplified by an amplifier (2), and the baggage (or the inspectiontarget) is moved toward the baggage exit (14) while irradiating thebaggage (inspection target) with the radio wave transmitted by a radiowave transmitting antenna (1) disposed in the magnetic shield (10).

The NQR signal from the baggage (inspection target) is detected by theSQUID (7) and is outputted from a SQUID electronic circuit (4) to alock-in amplifier (5) so that the signal of the same frequency as thatof the reference signal (taken from Table 1) from the radio wavetransmitter (3) is exclusively caught by the lock-in amplifier (5) andoutputted to a processor (6). The signal is stored, after about 1,000integrations, as data in the processor (6). The signal of thetransmitter is swept over the band 0.1 to 10 MHz so that the data of theprocessor (6) are displayed as the spectrum of 0.1 to 10 MHz. These dataare collated with the known spectra of explosives or illegal drugs sothat the substance is identified. If a substance is identified, awarning is issued. TABLE 1 NQR Spectrum of Typical Explosives Unit (MHz)TNT RDX HMX Nitrotoluene Trinitrotoluene Hexogen Octogen p-nitrotoluenem-nitrotoluene C₇H₅N₃O₆ C₃H₆N₆O₆ C₄H₈N₈O₈ p-C₇H₇NO₂ m-C₇H₇NO₂ 0.871 5.245.306 1.198 1.19 0.8604 5.192 5.068 0.911 0.91 0.845 5.047 3.737 0.94383.458 3.625 0.838 3.41 1.564 0.769 3.359 1.441 0.752 1.782 0.743 1.6880.716

-   -   (Source)    -   LANDOLT-BÖRNSTEIN    -   Vol. 20    -   Neclear Quadrupole Resonance Spectroscopy Data    -   Editors: K-H Hellwege and A M Hellwege    -   Springer-Verlag Berlin Heidelberg 1998

In a test of this device, 100 g of the TNT explosive was passed 5 cmbelow the SQUID. A signal of 1 pt (picotesla) could be caught, and thusthe explosive was detected. Likewise, this device can identify variouschemical substances such as explosives, poisons, chemicals, andnarcotics (such as heroin) so that it can be conveniently utilized forluggage inspections and customs inspections at airports.

INDUSTRIAL APPLICABILITY

The chemical substance detectors of the prior art were mostly the metaldetectors. However, the recent chemical substances to be detected areincreasingly non-metallic ones such as plastic bombs. The chemicalsubstance detecting device of the invention of this application can heapplied to such chemical substances as plastics and can also be reducedin size. Thus, this chemical substance detecting device can be expectedto be used widely as a chemical substance detector in the future.

1. A noncontact baggage inspection device capable of being reduced insize, characterized by comprising: an electromagnetic wave transmittingdevice including an electromagnetic wave transmitter and anelectromagnetic wave transmitting antenna having directivity; ahigh-temperature superconducting SQUID for receiving the NQR of nitrogenatoms resonating with the transmitted electromagnetic wave; ahigh-temperature superconducting SQUID controller; and a data processor.2. (canceled)
 3. A noncontact baggage inspection device of claim 1,characterized in that the electromagnetic wave transmitting antenna andthe high-temperature superconducting SQUID are disposed in a magneticshield made of double magnetic shielding plates.
 4. A noncontact baggageinspection device of claim 3, characterized in that the magnetic shieldis a metal box having a high magnetic permeability.
 5. A noncontactbaggage inspection device of claim 1, characterized in that a coolingmedium of the high-temperature superconducting SQUID is liquid nitrogen.6. A noncontact baggage inspection device of claim 1, characterized inthat the frequency of the transmitted electromagnetic wave is in theradio wave band of 0.1 to 10 MHz.
 7. (canceled)
 8. A noncontact baggageinspection device of claim 1, characterized in that a square wave istransmitted from the electromagnetic wave transmitting antenna, and thefrequency spectrum obtained by the quick Fourier analysis of thedetected signal of the high-temperature superconducting SQUID obtainedis compared with the spectral distribution of a chemical substanceobtained from a database.
 9. A noncontact baggage inspection device ofclaim 3, characterized in that a cooling medium of the high-temperaturesuperconducting SQUID is liquid nitrogen.
 10. A noncontact baggageinspection device of claim 4, characterized in that a cooling medium ofthe high-temperature superconducting SQUID is liquid nitrogen.
 11. Anoncontact baggage inspection device of claim 3, characterized in thatthe frequency of the transmitted electromagnetic wave is in the radiowave band of 0.1 to 10 MHz.
 12. A noncontact baggage inspection deviceof claim 4, characterized in that the frequency of the transmittedelectromagnetic wave is in the radio wave band of 0.1 to 10 MHz.
 13. Anoncontact baggage inspection device of claim 5, characterized in thatthe frequency of the transmitted electromagnetic wave is in the radiowave band of 0.1 to 10 MHz.
 14. A noncontact baggage inspection deviceof claim 3, characterized in that a square wave is transmitted from theelectromagnetic wave transmitting antenna, and the frequency spectrumobtained by the quick Fourier analysis of the detected signal of thehigh-temperature superconducting SQUID obtained is compared with thespectral distribution of a chemical substance obtained from a database.15. A noncontact baggage inspection device of claim 4, characterized inthat a square wave is transmitted from the electromagnetic wavetransmitting antenna, and the frequency spectrum obtained by the quickFourier analysis of the detected signal of the high-temperaturesuperconducting SQUID obtained is compared with the spectraldistribution of a chemical substance obtained from a database.
 16. Anoncontact baggage inspection device of claim 5, characterized in that asquare wave is transmitted from the electromagnetic wave transmittingantenna, and the frequency spectrum obtained by the quick Fourieranalysis of the detected signal of the high-temperature superconductingSQUID obtained is compared with the spectral distribution of a chemicalsubstance obtained from a database.
 17. A noncontact baggage inspectiondevice of claim 6, characterized in that a square wave is transmittedfrom the electromagnetic wave transmitting antenna, and the frequencyspectrum obtained by the quick Fourier analysis of the detected signalof the high-temperature superconducting SQUID obtained is compared withthe spectral distribution of a chemical substance obtained from adatabase.
 18. A noncontact baggage inspection device of claim 9,characterized in that the frequency of the transmitted electromagneticwave is in the radio wave band of 0.1 to 10 MHz.
 19. A noncontactbaggage inspection device of claim 10, characterized in that thefrequency of the transmitted electromagnetic wave is in the radio waveband of 0.1 to 10 MHz.
 20. A noncontact baggage inspection device ofclaim 9, characterized in that a square wave is transmitted from theelectromagnetic wave transmitting antenna, and the frequency spectrumobtained by the quick Fourier analysis of the detected signal of thehigh-temperature superconducting SQUID obtained is compared with thespectral distribution of a chemical substance obtained from a database.21. A noncontact baggage inspection device of claim 10, characterized inthat a square wave is transmitted from the electromagnetic wavetransmitting antenna, and the frequency spectrum obtained by the quickFourier analysis of the detected signal of the high-temperaturesuperconducting SQUID obtained is compared with the spectraldistribution of a chemical substance obtained from a database.
 22. Anoncontact baggage inspection device of claim 11, characterized in thata square wave is transmitted from the electromagnetic wave transmittingantenna, and the frequency spectrum obtained by the quick Fourieranalysis of the detected signal of the high-temperature superconductingSQUID obtained is compared with the spectral distribution of a chemicalsubstance obtained from a database.